Mercury May Be Shrinking Faster

A new study (lead author Gaku Nishiyama) using measurements from NASA's MESSENGER suggests Mercury has lost up to ~14 miles in diameter — about 30% more shrinkage than previous estimates — as its hot interior cooled and contracted over billions of years. The European–Japanese BepiColombo mission, arriving soon, carries a laser instrument that can directly test and refine that estimate. — If confirmed, a substantially larger planetary contraction will change models of Mercury's thermal evolution, tectonics, and how small rocky planets cool — with knock‑on effects for comparative planetology and interpretation of surface geology across the solar system.